Soldiers opened fire on Nigerian protesters in the Lekki district of the commercial capital Lagos on Tuesday, three witnesses told Reuters.
Protesters have staged demonstrations over allegations of police brutality for more than a week.
"They started firing ammunition toward the crowd. They were firing into the crowd," said Alfred Ononugbo, 55, a security officer. "I saw the bullet hit one or two persons," he said.
A Nigerian army spokesman did not immediately respond to requests for comment.
A Lagos state spokesman said he saw reports of a shooting on social media.
Inyene Akpan, 26, a photographer, said more than 20 soldiers arrived at the toll gate in Lekki and opened fire. He said he saw two people being shot.
Akinbosola Ogunsanya, a third witness, said he saw soldiers remove bodies.
A Reuters witness heard sirens and gunfire.
Authorities on Tuesday imposed a round-the-clock curfew on Lagos, which contains Africa's biggest city, in response to the protests, which the state governor said had turned violent.
The national police chief also ordered the immediate deployment of anti-riot forces nationwide following increased attacks on police facilities, a police spokesman said.